Process for alkyl ethers of alphahydroxycumene



2,777,000 Patented Jan. 8, 1957 PROCESS FOR ALKYL ETHERS F ALPHA- HY DROXYCUMENE' Thomas P. G. Shaw, Shawinigan Falls, Quebec, Canada,

assignor to Shawinigan Chemicals Limited, Montreal, Quebec, Canada, a corporation of Canada No Drawing. Applicationseptember- 27, 1954, Serial No. 458,693

Claims. (Cl. 260-611) This invention relates to the preparation of lower alkyl ethers of ai-hydroxycumene. These ethers may be designated alternatively as 2-alkoxy-2-phenylpropane, ocalkoxycumene, or as the alkyl ethers of u,ot-dimethylbenzylalcohol, or of dimethylphenylcarbinol, or of ahydroxycumene.

The preparation of the methyl ether of oz-hYdIOXY- cumene from a-chlorocumene has been reported by Ziegler and Schnell in Annalen 437, 254 (1924) and by Ziegler, Crossman, Kleiner, and Schafer in Annalen 473, 18 (1929) but it appears that none of the other alkyl others have hitherto been made. The necessary a-chlorocuniene has been prepared eg. by Klages (Berichte 35, 2638, 1902), from a-hydroxycumene which in turn has been made from acetophenone by the use of Grignard reagents. It is obvious that the prior art method for the preparation of the methyl ether of a-hydroxycumene, requiring intermediate Grignard reagents, dimethylphenyl carbinol, and oc-ChlOlOCUIIlBIlG, is not convenient or cheap.

In accordance with the present invention, the ether of a-hydroxycumene and a saturated aliphatic primary alcohol containing one to six carbon atoms is prepared by reacting wmethylstyrene and the said alcohol in the presence of hydrogen chloride in an amount at least stoichiometrically equivalent to the a-methylstyrene, and recovering the said ether from the reaction mixture. The equations for the reaction are as follows:

472 grams of u-methylstyrene (4 moles), 472 grams of methanol (14% moles) and 4 grams of dry cuprous chloride were placed in a stirred reaction vessel. Dry

hydrogen chloride gas was passed into the mixture at a rapid rate, while holding the temperature of the mixture at to C. and continuing for about 1% hours until about 150 grams of hydrogen chloride (4.1 mole) had been absorbed. The mixture was allowed to stand overnight and about 700 grams of water was added giving a two-layer system. Powdered sodium carbonate was then added with stirring until the system was neutral as indicated by the precipitation of the bluish green basic copper carbonate. This precipitate was filtered off, and the liquid layers were separated; then the organic layer was dried with calcium chloride, and fractionated at a pressure of 20 mm. mercury. The excess methanol, negligible amounts of methyl chloride, and some unreacted a-methylstyrene came over below 67 C. The crude product was recovered as a fraction at 67-82 C. at reduced pressure (about 20 mm.). This was further fractionally distilled to yield a substantially pure product which was analysed with an" infra-red spectrometer. Methyl ether of a-hydroxycumene found in all fractions amounted to 378 grams, which is 63.0% of the theoretical yield based on the total a-methylstyrene used, or 70.8% when corrected for recoverable ocmethylstyrene in the two fractions.

Example 2.T he butyl ether Example 1 was repeated in the same apparatus with the substitution of 1100 grams of butanol (14% moles) for the methanol. On fractionation of the dried organic layer at 20 mm. pressure the fraction below C. contained the excess butanol, unreacted rx-methylstyrene, sorne u-hydroxycumene, anda little of the butyl ether. The fraction at 100-120 C. was redistilled to give the pure product. Yield of butyl ether of a-hydroxycumene: 631 grams, which is 82.1% of the theoretical yield based on the a-methylstyrene used, without credit for recoverable a-methylstyrene,

7 Example .il-T he iso bulyl ether This was like Example 1 but using 890 grams of isobutanol in place of methanol. On distillation of the crude product at 20 mm. pressure a fraction B. P. C. was taken. The isobutyl ether of m-hydroxycumene accounted for in this and lower fractions amounted to 360 grams which is 47% of that theoretically possible Without credit for unreacted a-methylstyrene.

The corresponding ethers were also made using essentially the same method by substituting respectively npropyl alcohol, n-hexyl alcohol, and the mixture of amyl alcohols sold commercially as Pentasol in place of the other alcohols. The observed and calculated properties of the ethers were:

S ifi Refractive Ether B. P. at 20 mm. Hg Gravity Index 0. 9438 1. 4960 0. 930 1. 4916 0. 920 1. 4879 o. 012 1. .850 0. 93s 1. 4839 13 0. 03s 1. 4839 105 0. (1.8 mm. 0. 920 1.4823 Methylk. 78 0. (13 mm.) 0.9 15 (D420) 1.4981

1 The mixture of primary amyls from Pentasol. 2 The data reported in Annalen 437, 254 (1924).

The process is applicable to the lower saturated primary alcohols (both normal and branched-chain) containing one to six carbon atoms, but gives conversions which decrease with increasing molecular weights of the alcohol. Alcohols containing more than six carbon atoms give conversions to the ether which are too low to be of interest. The conversions are zero or negligible when using secondary or tertiary alcohols. It is desirable to carry out the reaction in the presence of excess of the alcohol being reacted; higher yields of the ether product are obtained when the alcohol is in excess than are obtained when stoichiometric amounts only are used. An excess of about 300% is quite satisfactory, although smaller excesses are also beneficial.

The reaction may be carried out at temperatures with in the range from about 9 C. to 50 C., the preferred range being from about 15 C. to 35 C. The hydrogen chloride gas is preferably added at a rate between one and two moles per hour per mole of a-methylstyrene when the temperature is 25 C., and may be added at higher rates at higher temperatures. The reactants are preferably kept dry, for water in an amount of about 3 1% by weight of the reactants reduces the conversion about 20%.

It is desirable to use an inhibitor of polymerization when the reaction is carried out at temperatures above 5 C. The preferred inhibitor is dry cuprous chloride; a concentration of one gram per mole of ot-methylstyrene is effective.

The lower alkyl ethers of ot-hydroxycumene are relatively high boiling liquids which, like many other ethers, are useful as solvents for specific resins, dyes, oils, etc., and fixatives for perfumes. Since they decompose to amethylstyrene on heating above about 150 C., the ethers can be a useful controllable source for the slow evolution of m-methylstyrene formed in situ in a reaction by heating one of the ethers above 150 C.

I claim:

1. A method of preparing the ether of e-hydroxycumene and a saturated aliphatic primary alcohol containing one to six carbon atoms comprising reacting under anhydrous conditions m-methylstyrene and the said alcohol in the presence of hydrogen chloride in an amount at least stoichiometrically equivalent to the a-methylstyrene, and recovering the said ether from the reaction mixture.

2. A process as claimed in claim 1, wherein the reaction is carried out at a temperature between 9 and +50 C.

3. A process as claimed in claim 2, wherein the reaction is carried out at a temperature between 15 and 35 C.

4. A process as claimed in claim 1, wherein the reaction is carried out in the presence of an inhibitor of polymerization.

5. A process as claimed in claim 4, wherein the inhibitor of polymerization is cuprous chloride.

6. A process as claimed in claim 1, wherein the alcohol is methanol.

7. A process as claimed in claim cohol is ethanol.

8. A process as claimed in'claim cohol is n-propanol.

9. A process as claimed in claim cohol is a primary butanol.

10. A process as claimed in claim 1, wherein the alcohol is a primary amyl alcohol.

1, wherein the al- 1, wherein the al- 1, wherein the al- Refereuces Cited in the file of this patent UNITED STATES PATENTS 2,056,915 Wulft et al Oct. 6, 1936 2,248,518 Stanley et al. July 8, 1941 2,468,982 Jansen May 3, 1949 

1. A METHOD OF PREPARING THE ETHER OF A-HYDROXYCUMENE AND A SATURATED ALIPHATIC PRIMARY ALCOHOL CONTAINING ONE TO SIX CARBON ATOMS COMPRISING REACTING UNDER ANHYDROUS CONDITIONS A-MEHTYLSTYRENE AND THE SAID ALCOHOL IN THE PRESENCE OF HYDROGEN CHLORIDE IN AN AMOUNT AT LEAST STOICHIOMETRICALLY EQUIVALENT TO THE A-METHYLSTYRENE, AND RECOVERING THE SAID ETHER FROM THE REACTION MIXTURE. 